The present invention concerns a method of monitoring an apparatus for the temperature control media supply of a tool of an injection molding machine having the features of the classifying portion of claim 1 and such an apparatus having the features of the classifying portion of claim 13.
In plastic processing and in particular in plastic injection molding it is important for the molding tool—referred for brevity as the tool—to be suitably temperature controlled, that is to say for certain temperatures to be kept constant in the tool over the production period by specifically targeted feed and discharge of heat. To achieve that passages are provided in the tool, through which a fluid—in most cases water—flows. Those passages are also referred to as temperature control conduits. Frequently a plurality of passages are supplied with a fluid at the same temperature so that those passages are fed from a feed and, after passing through the tool, are brought together to provide a return. That operation of dividing up and bringing together the fluid is generally effected in distributors in which for example a pressure sensor or through-flow sensors are arranged. As an example mention should be made here of AT 12213 U1 to the present applicant.
It is however also definitely usual for the temperature control conduits to be supplied individually with temperature control medium. A pressure or through-flow sensor is frequently also integrated in the temperature control system with that kind of supply.
Unobserved deposits or blockages entail the risk of a change in the thermal characteristics in the tool as far as damage to the tool in the event of too great a deviation from predetermined temperatures. That is the case both with temperature control media supply with individual temperature control conduits and also with a plurality of temperature control conduits, wherein the problem is worsened in the latter case as deposits and blockages are more difficult to detect.
The following method of identifying deposits or blockages in temperature control systems is known: the through-flow in each temperature control conduit is recorded at a given moment in time as a reference. To detect changes in the hydraulic system the through-flow in each temperature control conduit is again recorded at a later time. If changes can be detected in relation to the reference it is then assumed that there are changes or blockages.
That method has the disadvantage that the pressure in the feed and in the return must be constant. Fluctuations in pressure as frequently occur in practice cannot be taken into account. In practice therefore operation has to be interrupted to measure the quantitative flows and the tool has to be connected to suitable measuring devices to achieve the necessary accuracy.